Dark Green Vs. Light Green

I am testing the amount of Vitamin C in dark green vegetables and light green vegetables using an iodine indicator solution I had to make. I also investigated how important Vitamin C is and how green veggies can be a source of it too.
Safaa Asif
Grade 8



My hypothesis is that dark green vegetables will have a higher vitamin C content because they are full of nutrients such as fibre, folate, and certinoids. These vegetables also contain vitamin K, minerals, iron, and calcium. In addition, dark green vegetables act as an antioxidant in the body. This means that they can prevent or slow damage to cells. If dark green veggies are so beneficial to health, I hypothesize that they also have a great amount of vitamin C!




What are Vitamins

Vitamins are nutrients your body needs to function and fight off diseases. Fruits and vegetables are an excellent source of vitamins. There are 13 vitamins that are essential to your body working well.  There are 2 main types of vitamins, fat-soluble and water-soluble.


  • Vitamin A 

  • Vitamin D

  • Vitamin E

  • Vitamin K.


  • Vitamin C

  • Vitamin B1 (thiamine)

  • Vitamin B2 (riboflavin)

  • Vitamin B3 (niacin)

  • Vitamin B5 (pantothenic acid)

  • Vitamin B6

  • Vitamin B7 (biotin)

  • Vitamin B9

  • Vitamin B12 (cobalamin)


What is Vitamin C?


Pure vitamin C is a white, crystalline solid that is soluble in water. Its chemical name is ascorbic acid. Ascorbic acid is an organic compound, with the chemical formula of: C6H8O6

When someone thinks of vitamin C, pictures of oranges usually come to mind. This is because vitamin C is abundant in citrus fruits such as oranges, lemons, limes, and grapefruits. Lots of vegetables are an excellent source of vitamin C like, broccoli, cabbage, spinach, lettuce, parsley, capcicum, beans, and peas. But which one has the most? This test will help us find out.


Why is Vitamin C Important?

Vitamin C is an essential nutrient involved in the growth and repair of tissues in all parts of our body. It is used to form an important protein to make skin, tandents, ligaments, and blood vessels. Vitamin C protects the immune system, reduce the severity of allergic reactions and helps to fight off infections.

Deficiency of vitamin C can cause scurvy which includes tiredness and weakness, muscles and joint pains, and spots that look like tiny red-blue bruises on your skin. Other symptoms of deficiency can include dry skin, splitting hairs, swelling and discoloration of gums, sudden and unexpected bleeding from your gums, nose bleeds, poor healing of wounds, weight loss, tooth loss, and changes in your bones. It can also lead to shortness of breath, nerve problems, and high fever. 


What is Iodine?


Iodine is a dark purple lustrous solid element. It is used to treat and prevent iodine deficiency, and used as an antiseptic. It can be applied on wounds to disinfect the skin before surgery.                                             


Iodine in my Experiment

Iodine is relatively insoluble, so nothing can really dissolve in it, however this can be improved by complexing the iodine with iodide to form triiodide:

Triiodide can oxidize vitamin C to form dehydroascorbic acid:


Controlled Variables


  • Amount of iodine indicator solution
  • Amount of vegetables were kept same for all 4 samples
  • Amount of water added while blending


Manipulated Variables

  • Type of vegetable used

Responding Variables

  • Amount of vitamin C present in that vegetable
  • How many drops of juice was needed to clear the indicator solution.


Preaparing juice from the vegetables

  1. Since the veggies are solid we need to turn them into liquid before we can use the indicator solution on it

  2. Simply blend each of the vegetables in a blender

  3. Strain and keep the juices      


Preparing the Iodine Indicator Solution


An indicator solution is a substance that changes colour of the solution and responds to a chemical change.

  1. Mix together one teaspoon of cornstarch with some water to make a fine paste.

  2. Add this to 250 mL of boiling water, and allow it to boil for 1 minute

  3. Let it sit for 10 minutes to cool down

  4. Add a few drops of iodine tincture, it will turn blue, this will be your indicator solution


Testing the Vegetables


This method is called titration in which a solution of unknown concentration is reacted with a solution of a known concentration in order to find out about the unknown solution.

  1. With a dropper, add 10 ml of the iodine indicator solution (which you just made) into a test tube

  2. Add the juice samples dropwise using a pippet into the indicator solution. Count the drops carefully

  3. Clean the dropper and repeat the above for each sample

  4. Note how many drops were needed to discolor each sample.



What should happen is that if the vitamin C is present in the vegetable juice the purple color of the indicator will become pale purple or colourless. The vitamin C serves as a reducing agent and reduces iodine to iodide (colorless solution) ions. If there is no vitamin C or very little, the pale purple coloration will appear. The more drops needed to discolor the indicator shows how less vitamin C is present. This can be thought of as an indirect proportional relationship:


I observed that while I was performing the experiment I needed to measure the amount of iodine indicator solution very carefully so that it would be 10 mL for each vegetable sample. After that was taken care of I had to count the amount of drops of vegetable juice I was putting in the 10 mL of indicator solution because that is what I would base my results off of.

My chart & table....




The dark green vegetables were the winner. They were more successful in clearing out the iodine indicator solution in less drops, while the light green veggies took way more drops. In first place we had broccoli, then spinach, then cabbage, and finally, lettuce. The results were based off of which one cleared out the indicator solution better in fewer drops.



Firstly, I must say, MY HYPOTHESIS WAS CORRECT!! The dark green veggie samples showed more vitamin C than light green ones. Although my experiment was about green vegetables, this does not mean that dark green veggies have the most or are the only sources of vitamin C. Red and orange fruits and vegetables also contain high vitamin C. Since I was comparing between greens, I concluded my results based on the experiment. 

From this experiment we can infer that dark green veggies protects the immune system, reduce the severity of allergic reactions and helps to fight off infections because it contains vitamin C. Plus, why should we take vitamin supplements when we have these fruits and vegetables waiting to be eaten.




Nutrients provide nourishment. Proteins, carbohydrates, fat, vitamins, minerals, fibre, and water are all examples of nutrients. If people do not have the right balance in their diet, their risk of developing certain health diseases increases. In order to have a balanced diet,  we need to know what is in our food and how much our body needs of it. This is also helpful for those who buy expensive supplements for vitamins. Now that we know which veggies have more vitamin C, we can easily select which vegetable to include in our diet based on our needs.


Sources Of Error

Sources of Error

  • If the test tube, pipette, and blender had not been washed thoroughly, this could make the results less accurate
  • If the measurements in the indicator solution were wrong, it wouldn't be a proper indicator solution
  • The amount of water and vegetable used must be the same for all 4 samples to make the paste
  • The amount of indicator solution had to be the same for all 4 vegetables
  • I had to be careful while counting the drops
  • I had to be careful when measuring exactly 10 mL of indicator solution into the test tubes for each sample.



  • Firstly, I would like to thank my family for their continued help and support
  • Secondly, I must thank the website,  for giving me the idea of this amazing project, I would really encourage checking out more of their cool projects!
  • I should thank Safeway, because, well, I bought my supplies from there...
  • Well, I have to thank the sky for not collapsing on me, the ground for not causing an earthquake, or the wind creating a tornado or else I would not have been able to perform this experiment.